Oscillating knife-rotating anvil flying cutter

ABSTRACT

A flying cut-off knife for severing a continuously moving web of corrugated paperboard or the like to any length or lengths required; a length-setting switch directs a servo-system which effects close tolerance running changes in lengths cut taking into account board velocity and distance advanced; the servosystem controls a low inertia oscillating shaft having a pivotally retracting blade which rides against a mechanical rotation stop during cutting; prior to cutting the servo-system matches blade velocity to concurrently measured board velocity; cutting is simultaneous across the board; at the deepest point the blade penetrates through into the surface of a synchronously rotating anvil drum supporting the far side of the board; the principal parts of the invention are related by three parallel axes substantial superimposed.

United States Patent [1 1 Watson July 17, 1973 OSCILLATING KNIFE-ROTATING ANVIL FLYING CUTTER [75] Inventor: Raymond Slaysman Watson,

Baltimore, Md.

[73] Assignee: The Ward Machinery Company,

Cockeysville, Md.

{22] Filed: Nov. 3, I971 [21] Appl. No.: 195,216

[58] Field of Search 83/315, 317, 295, 83/337, 347, 363, 368, 369

3,039,713 6/1962 Nye 83/347 X Primary ExaminerFrank T. Yost Attrney.lohn F. McClellan, Sr.

[57] ABSTRACT A flying cut-off knife for severing a continuously mow ing web of corrugated paperboard or the like to any length or lengths required; a length-setting switch directs a servo-system which effects close tolerance running changes in lengths cut taking into account board velocity and distance advanced; the servo-system controls a low inertia oscillating shaft having a pivotally retracting blade which rides against a mechanical rotation stop during cutting; prior to cutting the servosystem matches blade velocity to concurrently measured board velocity; cutting is simultaneous across the [56] References cued board; at the deepest point the blade penetrates UNITED STATES PATENTS through into the surface of a synchronously rotating 1,809,668 6/1931 Bletso et al. 83/315 anvil drum supporting the far side of the board; the 1,944,7l0 H1934 Haswcll n /3 I 5 principal parts of the invention are related by three par- McNabb, Jl'. X anel axes substantial uperimposed ll8,327 8/l87l Arkell 83/347 3,038,362 6/1962 Porterfield 83/317 10 Claims, 8 Drawing Figures mouse KNIFE BAR SERVO CONTROL PROGRAMMER KNIFE SHAFT 56 SERVO CONTROL PATENIEUJUL 1 H915 3.745.864

sum 2 0F 5 INVENTOR RAYMOND SLAYSMAN WATSON BY zzwww g ATTORNEY PATENTEDJUHYIW I 3,745,864 sum 3 BF 5 FIGS INVENTOR RAYMOND SLAYSMAN WATSON ATTORNEY PAIENIE m 1 14915 SHEET 4 [IF 5 INVENTOR RAYMOND SLAYSMAN WATSON ATTORNEY Pmimwwm 3.745.864

sum 5 a? s I :52 FIG. 8 EEIIIEE I54 KNIFE BAR SERVO CONTROL PROGRAMMER KNIFE SHAFT SERVO CONTROL INVENTOR RAYMOND SLAYSMAN WATSON ATTORNEY OSCILLATING KNIFE-ROTATING ANVIL FLYING CUTTER This invention relates generally to machines for severing webs, and particularly to a servo-controlled knife and anvil flying cutter system for parting continuously moving rigid material such as corrugated paper board and the like.

Modern continuous laminating equipment produces corrugated paperboard faster than presently available devices can cut the board to the various arbitrary lengths required in commerce.

Available cutters can maintain suitable cutting rates within a restricted board-length range when constructed for that range, but no full-range, full-speed cutter is available.

Even within the restricted board-length range attainable with a typical cutter, substantial change from one board length setting to another requires shutting down operations.

The origin of these cutting problems lies in the nature of the work and in limitations of the old-art approach. Because corrugated paperboard is rigid and has sub stantial momentum at economical output rates, cutter velocity must match board velocity to produce a clean cutoff without damage to the cutter or the work.

The mechanism commonly used in this application comprises a rotary shear made of a pair of co-acting knives respectively mounted in parallel-opposed cylinders between which the board runs. This arrangement can be used at very high speeds, if the length of board required exactly matches the distance described by the circumference of knife swing.

However, market requirements for capabilities to make short runs of board to any given length in continuous production operations point up the limitations inherent in rotary shear design.

To compromise the conflicting requirements of matching cutter and boardvelocities while cutting to a length other than the nominal cut produced by uniform-rate rotation of the shear mechanism, in current practice rotation is accelerated during non-cutting parts of the cycle. Depending on relative proportions of specified board length and cutter swing, the accelerations are made to produce a net loss of intra-cycle time, or a net gain of intra-cycle time, with corresponding changes in board length cut.

To gain or lose appreciable percentages of intracycle time by accelerating conventional rotary shears demands such large and fluctuating power inputs that tapping momentum of the oncoming corrugated board has become common practice. Supplying peak demands in the shear cycle by linking to the line in this manner imposes heavy periodic loads on all the interconnected structures and modulates the advance rate of the work, making blade synchronization more difficult and increasing waste.

To avoid need for shutting down the line while adjusting rotary shears, and to expand available board length cutting ranges, two or more sets of rotary shears of different diameters can be superimposed and provided with means for diverting material to be cut from one to the other to reduce down-time.

In the present invention a wide range, running change length-cut provision is coupled with improved cutting tolerance provisions in a low stress, selfcontained cutter unit to provide corrugated paperboard production economies not previously possible.

The principle object of the present invention is, as indicated, to reduce the cost of corrugated paperboard and similar products.

In furtherance of the principal object, other objects are to provide a cutter for continuous production cutting of rigid web material:

which is adjustable at the flip of a switch to cut any length within a range of lengths encompassing most or all presently known commercial requirements, at board production rates of 700 feet per minute or more;

which cuts to closer tolerances than previously attainable;

which demands relatively modest peak power and average power inputs as compared with previous devices for the purpose;

which synchronizes and cuts as a self-contained unit, without imposing varying load requirements on the rest of the production line and without affecting board velocity;

which mounts the major parts pivotally, with axes arranged in compact, substantially over-and-under relation, afl'ording direct load transmission, rigidity, strength of mounting and economy of manufacture;

which requires minimum space;

which has a minimum of working parts, is economical to maintain, and which is reliable, durable, simple and safe to install, adjust and operate.

In typical embodiment the invention is characterized by a novel servo-controlled articulated-link oscillating knife opposed by a continuously rotating work supporting anvil, and by unique structural and operational features of these units.

The above and other advantages and objects of the invention will become more readily understood on examination of the following description, including the drawings, in which:

FIG. 1 is a perspective view partly broken away, of the input side of the invention;

FIG. 2 is an end view diagramming positions of the cutting mechanism of the invention;

FIG. 3 a a are successive-position diagrams similar to details of the FIG. 2 view;

FIG. 4 is a perspective view of a detail of the input side of the invention;

FIG. 5 is a front elevation diagram of details of the output side of the invention;

FIG. 6 is a perspective view of a portion of the output side of the invention;

FIG. 7 is detail of a portion of FIG. 1 partially broken away; and

FIG. 8 is a control system diagram.

In the various views, which will now be described in detail, like numerals indicate like parts.

FIG. I shows the invention 10 in partially broken away perspective looking down at a quartering angle onto the input side. Board B continuously advances through the cut-ofl'-knife system In in the direction indicated by the arrow, as laminating apparatus, not shown, produces the board.

Oscillating knife assembly 12, shown at the instant of cutting, pivots on the axis of knife shaft 14 periodically, swinging knife bar 16 downward and forward, driving blade 18 through the board, cutting the board to preselected lengths. Anvil drum 20 supports the board under the action of the blade 18, and receives the edge of the blade, which passes through the board into a resilient covering 22 on the cylindrical surface of the anvil drum. During cutting, the forward velocity component of blade 18 is synchronized with board velocity by a servo-system which is described later. Anvil drum surface velocity is synchronized with board velocity at all times through connection, not shown, between the anvil drum and the line drive which powers the board production machinery upstream.

Following cutting, the knife assembly disengages, retracts, reverses direction, and resets for the next cut under servo-control.

The prime movers responsive to the servo-system are a hydraulic motor 100 which oscillates knife shaft 14 through gearbox 102, and a hydraulic cylinder assembly 104 which retracts and extends knife bar 16 by rotating it relative to knife shaft 14 in a manner which will be described.

During normal operation, with board running through the line, the servo-system receives control data inputs at two milli-second intervals from two locations: tracking wheel 24 rides on the incoming board, providing inputs of board velocity and board lineal measurement to the servo-system through a wheel-linked resolver 106; drive linked resolver tachometer sensor system 108 supplies inputs indicating rotative position and velocity of knife shaft 14, to which blade position is related by an open loop system described later.

To provide sustaining inputs to the servo-system during periods when board is not present, provision is made for the periphery of tracking wheel 24 to drop below the board plane onto roller 30. Roller 30 connects through gears 32, 34 with feeder nip-roll gears 36, 38, which in turn connect through gears 40, 42, 44 with the line drive, thus effectively providing, when no board is present, a surface rate for the tracking wheel equating to board velocity. This provision avoids slippage errors which would otherwise occur on resumption of board feed, and maintains the other parts of the system in operating equilibrium. Tracking wheel 24 is preferably suspended by an arm 26 pivoted to the frame of the unit as at 28.

The frame of the unit includes an overhead transverse beam structure 48 supported by spaced vertical side-frames 50 and 52 which are connected at the bottom by a base 54.

The side frames journal between them anvil drum 20, roller 30, input nip-rolls 56, 58, and the other rollers of the cutter unit. The overhead beam structure 48 supports the oscillating knife assembly 12.

Three axes define operation of the oscillating knife assembly; two of the axes are fixed in plane-parallelspaced relation and the third axis swings in parallel relation between two fixed axes.

The top axis, x, defines rotation of knife shaft 14.

The bottom axis, 2, defines the rotation of anvil drum 20.

The intermediate axis, y, swings about axis x of the knife shaft, and defines the rotation of knife bar 16, relative to knife shaft 14 which allows blade 18 to extend on the working half cycle and to retract clear of the work on the resetting half cycle.

FIG. 2, a diagrammatical section taken at 2-2, FIG. 1, shows the relation of the knife assembly 12 to adjacent elements of the system, and indicates positions a a which the knife assembly passes through during the working or cutting half-cycle of oscillation.

Overhead beam structure 48 supports knife shaft 14 pivotally about axis x by means of aligned journal structure represented in the Figure by pillow block 60.

Knife shaft 14 supports knife bar 16, and blade 18 integrally carried by the knife bar, pivotally about axis y by means of knife bar axle structure represented in the Figure by axle 68. In the cutting mode, typified by position 0, blade 18 is held substantially in-plane with axes x and y.

Anvil drum 20 is cylindrical and is rotatively sup ported about the cylinder axis, shown foreshortened at z, by bearings which are not shown. Board B passes between blade 18 and resilient covering 22 on the periphery of the anvil drum.

The entire apparatus extends parallel with the three axes x, y and z, perpendicularly across the full width of the board.

In operation, cutting is simultaneous across the full width of the board. As the work advances in the direction indicated by the straight arrow, the knife assembly 12 holds in position a until the intended cut point on the board approaches within a servo-system determined distance, from the left in the diagram. Then the knife assembly leaves the rest position at a and accelerates until it reaches position b, at which time the forward component of blade velocity matches board velocity.

Blade 18 enters the board at board velocity, maintains board velocity through the vertical position at c and until disengagement with the board, between illustrated positions 0 and d.

Through the center part of the cutting stroke the edge of the knife blade embeds in the resilient (preferably polyurethane) layer 22 covering anvil drum 20, assuring an even, complete cut through the board.

Following disengagement and during the remainder of the working half-cycle, as knife shaft 14 approaches the turnaround position at e, the servo-system rotates knife bar 16 relative to knife shaft 14 in the direction of travel. At position e, relative rotation of the knife bar with respect to the knife shaft reaches a limiting misalignment angle of about 44. This angle between the plane of the blade and the plane passing through axes x and y is maintained during much of the resetting halfcycle to provide clearance as the blade returns past the board, as shown in FIG. 3.

FIG. 3 is a section taken at 3-3, FIG. 1, showing somewhat more structural detail of the knife shaft to knife bar engagement than FIG. 2.

FIG. 3 indicates in developed sequence the cutting stroke positions a e which were superimposed in FIG. 2, and additionally shows typical retum-stroke positions f, g, h, i passed through in the clockwise halfcycle, and a, the starting position for the next cycle.

At this point a further structural feature of the knife assembly should be noted, the limiting mechanical contact provided on rotative engagement of step 84 of the knife shaft with step 86 of the knife bar, as in FIGS. 3 a, b and c. This limiting contact helps compromise conflicting requirements of the design. Because of the high accelerations involved, the knife shaft and knife bar are designed to exhibit the lowest practicable inertia in operation. On the other hand, the need to make a simultaneous cut across the width of the board imposes high instantaneous loads on the knife bar structure and on the servo-system which controls rotation of the knife bar relative to the knife shaft. The limiting contact between steps 84 and 86 is preferably arranged to occur at a slightly overcenter rotative position in that the angle between the blade plane and the plane passing through axes x and y is slightly less than 180 on the side of the limting contact. This arrangement tends to lock knife bar 16 in the cutting position, relieving the load on the open-loop portion of the servo-system during cutting. Also, in conjunction with the provision shown in which the direction of knife bar rotation to extend the blade is made counter to the direction of oscillation during cutting, the arrangement somewhat relieves accelerative loads on the knife bar actuation system adjacent the positions of oscillation reversal.

FIG. 4, a detail of the FIG. 1 view partially broken away, indicates inter-related details of the actual structure and extent of the limiting steps in the knife shaft and knife bar, of the construction of the knife shaft, and of the drive inputs to the knife shaft and the knife bar. FIGS. 4 and 5 will be described in conjunction.

FIG. 5 is a front elevation diagrammatical detail viewed at the input side of the knife assembly.

FIGS. 4 and 5 show that one set of steps 84, 86 is provided at each of eight equally spaced, co-axial bearings 70, 72, 74, 76, 78, 80, 82, 84, connecting the knife bar 16 and knife shaft 14. The spaced bearings provide practically continuous cutting-load transmission between the knife bar and the knife shaft without overconstraint sufficient to affect pivoting, and the steps provide effectively local support throughout the length of the knife bar during initial acceleration and cutting.

The unique composite structure of the knife shaft 14 satisfies requirements of low rotational inertia, torsional and bending stiffness, local transmission of loads, and economy and facility of construction.

Five in-line stub axles 88, 90, 92, 94, 96, rotatively support the four tubular elements 110, 112, 114, 116 to five pillow blocks 60, 62, 64, 66, 102. The central pillow block 102 serves also as the gearbox of the knife shaft drive, providing rigid center-drive connection. The outboard stub axles 88, 90, 94 and 96 are integrally affixed at the ends to the tubular elements, as by being force-fitted and pinned, or by being cast in place. The tubular elements are preferably cast aluminum and the stub axles steel. The central stub axle is preferably taper-fitted and pinned to the adjacent tubular elements 112 and 114.

As indicated, and as further described below in reference to FIG. 7, sector gear 46, FIG. 4, is the drive input provided to oscillate knife shaft 14.

Actuator 104 oscillates knife bar 16 with respect to knife shaft 14. Hydraulic cylinder 118 of the actuator is joumalled to block 120 affixed to knife shaft 14 and piston 122 is joumalled to block 124 affixed to knife bar 16.

Knife bar 16 mounts blade 18 in the manner indicated in FIGS. 4 and 5. Slot 126 (FIG. 4) in the knife bar receives the blade and spaced machine screws 128 pass transversely through the knife bar and the blade, securing the two together. This arrangement allows precise shim-adjustment of the blade in the slot to be made, if desired. Initial alignment of the blade with the anvil drum is preferably made by shifting the anvil drum axis 2, using eccentric bearing block structure, not shown.

FIG. 6 is a perspective view of details of the output side of the invention showing how the economy and arrangement of parts provides clear, direct access on this side, as well as on the input side, for installation, adjustment, inspection, and blade changing, when the niprolls are removed.

FIG. 7 is a perspective detail of the input side similar to the FIG. 4 view, partially broken away to show connection of drive motor to knife shaft 14 and to sensor assembly 108. Spur gear on the motor output shaft connects through reducing idler gearing 132, 134 to sector gear 46 on the knife shaft.

Sensor assembly 108 (which attaches to the gear box as indicated in FIG. 6) connects axially through splined shaft 136 with the output shaft of the drive motor 100. The sensor assembly includes tachometer-reducer section 138, coupling section 140 and resolver section 142.

FIG. 8 is a block diagram schematically relating inputs and outputs of the control system of the invention. Altogether the control system receives inputs from three locations: length-of-cut setting switch 152, board velocity and linear measurement tracking wheel resolver 106, and the knife shaft position and velocity sensing resolver-tachometer couple at 138 and 142. The control system sends command signals to two locations: the knife shaft motor 100 and the knife bar actuator 104.

Required length-of-cut is set into programmer 154 through manually operated switch 152. Response of the system to the setting is automatic, and for practical purposes, instantaneous. Using data on board velocity and length supplied by tracking wheel resolver I06, and on knife shaft position and velocity supplied by knife shaft resolver 138 and tachometer 142, programmer 154 and knife shaft servo-control 156 signal knife shaft valve 158, which is supplied from hydraulic pressure source S. In response, the valve admits fluid to motor 100, as required to rotate knife shaft 14 for tracking and cutting on the schedule set. Feed-back supplied to the knife shaft servo-control through the circuit indicated regulates the response of the system according to established practice.

Position'of knife bar 16 relative to knife shaft 14 is programmed through an open loop circuit, as schematically indicated in the connection from the programmer through knife bar servo-control 160 to knife bar valve 162. Knife bar valve 162, in turn, appropriately regulates flow to knife bar actuator 104, producing a high response rate at intermediate positions coupled with a low rate or creep near the rotatiive limits of the knife bar relative to the knife shaft.

In summary, it can be seen that the low-radius, lowmass design of the pivotally oscillating, servocontrolled knife assembly of the system inventively complements the high-radius, large wear area, massive, continuously rotating anvil of the system in such manner as to provide never before attained flexibility and precision while at the same time isolating the cutoff function from transients in and demand on associated equipment in the line.

It will be understood that the invention is not limited to the exemplary details of material, sensing, motive power and motor arrangement given.

Obviously many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed and desired to be secured by United States Letters patent is:

l. A flying knife for synchronously cutting continuously translating material, comprising: cutting means, means for oscillating the cutting means; means for periodically pivoting the cutting means to oppositely pointing alignment with the oscillating means axis, thereby periodically extending the cutting means for cutting; means for supporting translating material at a position for cutting on oscillation of the extended cutting means and for clearing on oscillation of the cutting means when not extended; means for adjustably synchronizing operation of the cutting means with translation of material for cutting, including: means for measuring the velocity and distance of translation of material, means for measuring the angular velocity and position of the oscillating means, means for setting cut length required, and means responsive to all said measuring and setting means for thereby controlling velocity and repetition rate of said oscillation of the cutting means.

2. A flying knife as recited in claim 1 wherein the means for measuring velocity and distance of translation of material includes a tracking wheel, a support for holding the tracking wheel in contact with translating material, a roller adapted for rotating in synchronism with material translation velocity, and a connection adapted to bring the tracking wheel and the roller in contact in the absence of material for tracking.

3. A flying knife as recited in claim 1, wherein the means for adjustably synchronizing operation of the cutting means includes means for adjusting extension of the cutting means in proportion to position, direction of rotation, and oscillation rate of the oscillating means.

4. A flying knife for cutting continuously moving material, comprising: a shaft having an axis of rotation, a first actuator adapted for oscillating the shaft about said axis of rotation, a blade having pivotal connection with a radial portion of the shaft, a second actuator adapted for pivoting the blade away from and toward the shaft, thereby radially extending and retracting the blade with respect to the shaft; a stop adapted for limiting pivotal motion of the blade in one direction with the blade in the extended position; a roller adapted for continuous rolling, a frame positioning the roller to support continuously moving material for cutting between said roller and the blade on oscillation of the shaft with the blade in the extended position; a control system having a sensor assembly for measuring velocity and travel of continuously moving material and adapted through connection with the first actuator for adjustably proportioning the velocity and frequency of oscillation of the shaft in response to said measurements, and means for causing the second actuator to extend and retract the knife blade repetitively in respective successive half cycles of shaft oscillation.

5. A flying knife as recited in claim 4, wherein the shaft axis and the blade pivot axis are spaced in parallel relation with the roller axis, with the blade pivot axis positioned intermediate the distance of said spacing.

6. A flying knife as recited in claim 5, wherein the roller has a yielding surface and wherein the roller is positioned to receive a portion of the blade in said yielding surface during cutting.

7. A flying knife as recited in claim 6, and means for continuously rotating the roller at a rate synchronous with velocity of material to be cut.

8. A flying knife as recited in claim 4, wherein the control system sensor assembly includes means for tracking moving material, wherein a driven roller is provided adjacent said means for tracking moving material, and whereas a movable connection is provided for bringing together the means for tracking moving material and the driven roller in the absence of moving material.

9. A flying knife for synchronously cutting continuously translating material, comprising cutting means, means for oscillating the cutting means including a shaft having intermediate the length thereof a relatively small diamter portion adapted for receiving bearing support and oscillatory drive, with a relatively large diameter tubular portion outboard each side of the relatively small diameter portion, said relatively large diameter tubular portions having pivot structure coaxially aligned along a peripheral portion thereof for pivotally mounting said cutting means; means for periodically pivoting the cutting means to oppositely pointing alignment with the oscillating means axis, thereby periodically extending the cutting means for cutting; means for supporting translating material at a position for cutting on oscillation of the extended cutting means and for clearing on oscillation of the cutting means when not extended, and means for adjustably synchronizing operation of the cutting means with translation of material for cutting.

10. A flying knife as recited in claim 9 wherein the cutting means comprises a knife bar having a slot, a blade protrusively affixed in the knife bar slot, and pivot structure along the knife bar adapted for pivotal co-action with said shaft pivot structure. 

1. A flying knife for synchronously cutting continuously translating material, comprising: cutting means, means for oscillating the cutting means; means for periodically pivoting the cutting means to oppositely pointing alignment with the oscillating means axis, thereby periodically extending the cutting means for cutting; means for supporting translating material at a position for cutting on oscillation of the extended cutting means and for clearing on oscillation of the cutting means when not extended; means for adjustably synchronizing operation of the cutting means with translation of material for cutting, including: means for measuring the velocity and distance of translation of material, means for measuring the angular velocity and position of the oscillating means, means for setting cut length required, and means responsive to all said measuring and setting means for thereby controlling velocity and repetition rate of said oscillation of the cutting means.
 2. A flying knife as recited in claim 1 wherein the means for measuring velocity and distance of translation of material includes a tracking wheel, a support for holding the tracking wheel in contact with translating material, a roller adapted for rotating in synchronism with material translation velocity, and a connection adapted to bring the tracking wheel and the roller in contact in the absence of material for tracking.
 3. A flying knife as recited in claim 1, wherein the means for adjustably synchronizing operation of the cutting means includes means for adjusting extension of the cutting means in proportion to position, direction of rotation, and oscillation rate of the oscillating means.
 4. A flying knife for cutting continuously moving material, comprising: a shaft having an axis of rotation, a first actuator adapted for oscillating the shaft about said axis of rotation, a blade having pivotal connection with a radial portion of the shaft, a second actuator adapted for pivoting the blade away from and toward the shaft, thereby radially extending and retracting the blade with respect to the shaft; a stop adapted for limiting pivotal motion of the blade in one direction with the blade in the extended position; a roller adapted for continuous rolling, a frame positioninG the roller to support continuously moving material for cutting between said roller and the blade on oscillation of the shaft with the blade in the extended position; a control system having a sensor assembly for measuring velocity and travel of continuously moving material and adapted through connection with the first actuator for adjustably proportioning the velocity and frequency of oscillation of the shaft in response to said measurements, and means for causing the second actuator to extend and retract the knife blade repetitively in respective successive half cycles of shaft oscillation.
 5. A flying knife as recited in claim 4, wherein the shaft axis and the blade pivot axis are spaced in parallel relation with the roller axis, with the blade pivot axis positioned intermediate the distance of said spacing.
 6. A flying knife as recited in claim 5, wherein the roller has a yielding surface and wherein the roller is positioned to receive a portion of the blade in said yielding surface during cutting.
 7. A flying knife as recited in claim 6, and means for continuously rotating the roller at a rate synchronous with velocity of material to be cut.
 8. A flying knife as recited in claim 4, wherein the control system sensor assembly includes means for tracking moving material, wherein a driven roller is provided adjacent said means for tracking moving material, and whereas a movable connection is provided for bringing together the means for tracking moving material and the driven roller in the absence of moving material.
 9. A flying knife for synchronously cutting continuously translating material, comprising cutting means, means for oscillating the cutting means including a shaft having intermediate the length thereof a relatively small diamter portion adapted for receiving bearing support and oscillatory drive, with a relatively large diameter tubular portion outboard each side of the relatively small diameter portion, said relatively large diameter tubular portions having pivot structure co-axially aligned along a peripheral portion thereof for pivotally mounting said cutting means; means for periodically pivoting the cutting means to oppositely pointing alignment with the oscillating means axis, thereby periodically extending the cutting means for cutting; means for supporting translating material at a position for cutting on oscillation of the extended cutting means and for clearing on oscillation of the cutting means when not extended, and means for adjustably synchronizing operation of the cutting means with translation of material for cutting.
 10. A flying knife as recited in claim 9 wherein the cutting means comprises a knife bar having a slot, a blade protrusively affixed in the knife bar slot, and pivot structure along the knife bar adapted for pivotal co-action with said shaft pivot structure. 